Unsaturated polyesters find extensive utility in a wide variety of applications. Being essentially organic in nature such polyesters are all combustible to greater or lesser extent. Many different approaches and techniques have been developed to improve the resistance of polyesters to ignition or to propagation of flame. Typical are the use of inorganic fillers, organic fire retardants, and the chemical modification of the diacid, the diol or the reactive diluent employed.
In recent years there has been developed a class of dicyclopentadiene modified unsaturated polyesters. These polyesters have a unique spectrum of properties, but, as expected, are combustible. One technique employed to improve their fire resistance is to brominate the pendant cyclopentene double bond of the dicyclopentadiene in the polyester. That generally results in less than the necessary amount of bromine for many applications. It has been found that the necessary bromine can be incorporated by including a brominated reactive diluent such as dibromodicyclopentadiene acrylate. However, that requires a separate bromination step.
In copending patent application U.S. Ser. No. 283,315 filed July 14, 1981 there is described a process whereby dicyclopentadiene acrylate or its equivalent could be blended with the dicyclopentadiene modified unsaturated polyester and both components brominated to the desired extent without causing bromination of the other parts of the molecule.